Send As for Shared Mailbox in Office 365

[BrianDoc770]

Good Afternoon, 

We are in the process of migrating our user base to Office365, so right now we are in a hybrid mode. 

I have a user, her mailbox is still on-prem.  OnPrem we have Exchange 2016.   She was recently given Full Access and Send As permissions to a shared mailbox that was migrated to Exchange Online.  

Now she is unable to send from that mailbox,  or forward from that mailbox to hers.  We have seen this recently where the shared mailbox is on-prem and user mailbox migrated and we would run 

Add-ADPermission -Identity EXO1 -User ONPREM1 -AccessRights ExtendedRight -ExtendedRights "Send As" from On-Prem Exchange Powershell and then run:

Add-RecipientPermission -Identity ILiketoSmile -Trustee smileyg@chop.edu -AccessRights SendAs in Exchange Online PS. 

We have tried to have her go to on-prem webmail, login with shared mailbox credentials, click the redirect link and still did not work.  Had her login to a VDI with that account, still would not open. I believe we are going to migrate her account, but even at that, we are looking at 3-5 day turnaround time.   

Was wondering if anyone might know of a workaround we can put into place.  or a script that we can try to run to keep her in business while we do the migration. 

Thank You

Brian Dougherty

[#2 · Accepted solution]

@BrianDoc770 Hi, on the run but see if this can assist https://docs.microsoft.com/en-us/exchange/troubleshoot/shared-mailboxes/cannot-access-mailbox

[#3]

@ChristianBergstrom - Good Morning

Thank you for article link.  Spoke to my lead and we are just going to migrate her to Office365

[#4]

Hi!

I do have the same problem but my shared mailbox is On-Premise and my own mailbox is in Exchange Online.

I have configured a full hybrid configuration and free/busy is working. Also migration to and from is working fine.

How can I make "Send As" able? (Full access is working)

On-Premise:
Sharemailbox

ExO:
User

User needs send as permission in de sharemailbox.